He or she may recommend that you go to a hospital emergency department.

If you are unable to reach your health care provider and are concerned about your symptoms, go to the emergency department.

Severe reactions, including symptoms such as difficulty breathing, dizziness or light-headedness,

or tightness or choking in the throat, require treatment in an emergency department.

Even mild symptoms that are not improving or are getting worse require evaluation in an emergency department.

Do not attempt to drive yourself to the hospital. If no one is available to drive you immediately, call 911 for emergency medical transport. While waiting for the ambulance to arrive, start self-treatment.

Self-Care at Home

For localized hives or other mild skin reactions

Take cool showers or apply cool compresses.

Wear light clothing that doesn't irritate your skin

Take it easy. Keep your activity level low.

To relieve the itching, apply calamine lotion or take over-the-counter antihistamines, such as diphenhydramine (Benadryl) or chlorpheniramine maleate.

For all other reactions, especially severe reactions, self-treatment is not recommended. Have a companion drive you to the hospital emergency department, or call 911. Here's what you can do while waiting for the ambulance:

Try to stay calm.

If you can identify the cause of the reaction, prevent further exposure.
Take an antihistamine (1-2 tablets or capsules of diphenhydramine [Benadryl]) if you can swallow without difficulty.

If you are wheezing or having difficulty breathing, use an inhaled bronchodilator such as albuterol or epinephrine (Primatene Mist) if one is available. These inhaled medication dilate the airway.

If you are feeling light-headed or faint, lie down and raise your legs higher than your head to help blood flow to your brain.

If you have been given an epinephrine kit, inject yourself as you have been instructed. The kit provides a premeasured dose of epinephrine, a prescription drug that rapidly reverses the most serious symptoms (see Follow-up).

Bystanders should administer CPR to a person who becomes unconscious and stops breathing or does not have a pulse.

If at all possible, you or your companion should be prepared to tell medical personnel what medication you have taken that day, what you usually take, and your chronic disease history.

The allergist will ask you about the sequence of events that led to the reaction and record a thorough dietary and medical history.

He or she may use special tests to find out which food is responsible for the allergic reaction.
By conducting these tests, the allergist can identify the food responsible for the chronic disease and help create a plan for avoiding that particular food.

Skin test: Dilute extracts of various foods are placed on the skin. The allergist looks for the formation of a bump on the skin after 10-20 minutes. Swelling at the site of the test can mean that you are allergic to that particular food.

Blood test: This may be used to check for antibodies against specific food allergens. These results are confirmed with the oral challenge test in which small doses of the suspected food are given in a mixture of different foods to look for a reaction. If symptoms develop, then you are proven to have allergies to the particular food.

Elimination diet: With this test, you stop eating foods that may be triggers. Gradually these foods are re-introduced back into the diet. The allergist will then be able to pinpoint the chronic disease-causing food if a reaction occurs.

Individuals with food allergies and their family members should have a clear plan of action in case of an accidental ingestion of the offending food. Emergency medication such as antihistamines and epinephrine should always be available.

Susceptible people should keep with them an epinephrine kit (brand names are Epi-Pen, Ana Kit, Ana Guard) in case of exposure to the allergen.
The kit contains a premeasured dose of epinephrine in an easy-to-use syringe for self-injection.
You inject the medicine into your thigh as soon as you feel an allergic reaction coming on.
Even if you inject yourself with epinephrine, you should still proceed immediately to a hospital emergency department.

It is not unusual for a reaction to abate and then return within a few hours. Even if you require no further treatment, you should remain at the hospital until 4-6 hours after the beginning of the reaction.

Be prepared to deal with an anaphylactic reaction if you are exposed to the culprit food again. If you have had a severe reaction before, carry your epinephrine kit.
Never underestimate the danger of an allergic reaction.

The shots do not treat symptoms, but by altering the immune response they prevent future reactions. (This is referred to as immunotherapy.)
Treatment involves a series of shots, each containing a slightly greater amount of the antigen(s) that cause the reaction.
Ideally, the person will become "desensitized" to the antigen(s) over time.
These are still under investigation and have not been proven to prevent allergic reactions.
The effectiveness of shots varies by individual.